Field of the Invention
The present invention relates to a planetary gear train of an automatic transmission for a vehicle. More particularly, the present invention relates to a planetary gear train of an automatic transmission for a vehicle which improves power delivery performance and fuel efficiency according to multiple speed stages as a consequence of achieving nine forward speed stages using a minimum number of constituent elements and improving silent driving by using driving point in a low engine speed.
Description of Related Art
The recent increase in oil prices has caused car makers to meet global demands for improving fuel efficiency. As a result, research is being conducted on engines in terms of reducing weight and improving fuel efficiency by down-sizing, and research is also being conducted to ensure both drivability and competitiveness for maximizing fuel efficiency by implementing an automatic transmission with multiple speed stages.
However, in the case of the automatic transmission, the number of internal components is increased as the number of gear shift stages is increased, and as a result, the automatic transmission may be difficult to mount, the manufacturing cost and weight may be increased, and power transmission efficiency may be deteriorated.
In this aspect, in recent years, a transmission capable of achieving more than 8-speeds tends to be implemented and is mounted on the vehicles, and the research and development of a planetary gear train capable of implementing more speed stages has also been actively conducted.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.